Note: Descriptions are shown in the official language in which they were submitted.
33~9
Background of the Invention
This invention relates to the field of air cleaners
and particularly to two-stage air cleaners which include a first,
centrifugal cleaning stage or precleaner, for removing larger
particles, and a second, filtering stage, in which the filtering
means includes an outer, principal filter enclosing an inner,
"safety" filter. In such cleaners the principal factor deter-
mining the pressure drop across the cleaner is the size of the
outlet opening. Since this opening can be no larger than the
size of the smallest component of the filtering means, the desir-
ed low pressure drop must frequently be achieved at the cost of
an increased size of the cleaner as a whole. This factor is
- further complicated by the fact that the effectiveness of the
centrifugal cleaner stage is a function of the volume of air
available outside the filtering means and near the collector for
larger particles.
Summary of the Invention
The present invention provides two-stage air cleaner
for removing, from a stream of air, solid particles in a range
of sizes, comprising, in combination:
a housing, generally cylindrical about an axis extend-
ing between first and second closed ends thereof, said first end
having an annular inward step, the housing having a lateral in-
let opening near said first end, an axial outlet opening of
less diameter than said housing in said first end, and particle
collecting means at said second end;
filtering means in said housing including a hollow
body having the shape of a frustum of a circular cone with a
larger end directed toward said outlet opening, and of generally
the same diameter as said housing, and a smaller end directed
away from said outlet opening, said body being of porous paper
pleated in alignment with lines defined on said frustum by
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planes passing through the axis thexeof, so that the pleats are
more open at said larger end than at said smaller end;
means supporting said filtering means axially in said
housing with said larger end surrounding said outlet opening, so
that the space between said housing and said filtering means is
greater near said second end of said housing than near said
first end thereof, including means closing the smaller end of
said body and means urging said body toward said first end of
said housing;
sealing means including resilient means between said
larger end of said body and said first end of said housing, for
preventing passage of air through said housing from said inlet
opening to said outlet opening except through said filtering
means, said sealing means including a resilient annulus connected
to the larger end of said filtering means, and having first and
second portions severally engaging said first end of said housing
and said annular inward step;
and means for imparting to air entering said cleaner
at said inlet opening a vortical component of motion around said
filtering means and toward said collecting means, and for pre-
venting direct impingement of said entering air on said more open
pleats.
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In a particular embodiment, hereinafter described
in more detail, the filtering means comprises a primary filter
of porous paper pleated in alignment with lines defined on the
frustum by planes passing through the axis thereof, so that the
pleats are more open at said larger end than at said smaller end,
and further includes a safety filter comprising porous material
in the form of a frustum of a circular cone having a larger end
dlrected toward and at least as large as the outlet opening but
smaller than the larger end of the primary filter, and a smaller
end directed away from the outlet opening and smaller than the
smaller end of the primary filter; and means supporting the
safety filter coaxially within the primary filter. The structure
may include baffle means in the housing outside of the filtering
means for preventing direct impingement, on the primary filter,
of the air entering the housing, and for imparting to said air
a vortical component towards the other end of the housing, to
comprise with the collecting means a precleaning stage for the
air cleaner to remove larger particles from the air.
In this embodiment, the invention improves both the
pressure drop through the cleaner and the effectiveness of the
precleaner, by changing the configuration of the principal and
safety filters, making them conical, tapering away from the
cleaner outlet opening. This maximizes both the available dia-
meter of the outlet opening, and the volume between the principal
filter and the cleaner housing near the particle collector, for
any given housing diameter. The arrangement also includes an
improved seal between the principal filter and the end of the
housing, to ensure that no air passes from the inlet to the out-
let of the cleaner without having passed through at least the
safety filter, which improved seal also functions to clean and
remove dirt from the housing wall when the filter is serviced.
The invention also embodies an improved structure by which in-
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sertion and removal of filtering means such as a safety filter
is made simpler, quicker, and more certain, ~ithout the use of
tools.
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Brief Description of the Drawing
In the drawing, FIGURE 1 is a view in elevation of an air cleaner
including the invention, parts being broken away for clarify of illustration;
FIGURE 2 is an end view of the same cleaner, parts also being
broken away;
FIGURES 3, 4 and 5 are enlarged fragmentary detailed views of
portions of the invention;
FIGURE 6 is a view in elevation of an air cleaner embodying the
invention, parts being broken away for clarity of illustration;
FIGURE 7 is an end view of the same cleaner seen from the left of
FIGURE 6, parts also being broken away; and
FIGURE 8 is an exploded detailed view of a portion of the invention.
Description of the Preferred Embodiments
In the drawing, an air cleaner 10 is shown to have a housing 11
which is generally cylindrical about an axis 12 extending between a closed
end 13 and an open end 14. Housing 11 has a lateral opening 15 near closed
end 13, to which is fitted the usual inlet connection member 16. Closed
end 13 includes a permanent closure member 17 having an annular inward step
20 and an axial outlet opening 21 with a connection tube 22.
A support yoke 23 has a pair of legs 24 and 25 which diverge to
be secured to the inside of tube 22 as shown at 26: the yoke extends along
axis 12 and terminates in an axial externally threaded member 27, which
serves as the outboard support for filtering means including a safety
filter 30 and a principal filter 31.
Safety filter 30 comprises a hollow porous body 32 having a cen-
tral axis of symmetry coincident with axis 12. Body 32 is not cylindrical
: but conical; it tapers from a maximum diameter near closure member 17 to a
minimum diameter near member 27. The larger end of filter 30 is secured in
: an annular mounting member 33 having an internal diameter to fit over the
legs of yoke 23, and carrying a resilient ring 34 to seal against closure
17 around opening 21. The smaller end of body 32 is secured to a disk 35
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which closes the end of the safety filter except for a central aperture 36
to pass member 27 and the shoulder of a wing nut 37 on member 27 which may
be tightened to sealingly secure filter 30 coaxially in housing 11.
Principal filter 31 is also conical, tapering from a maximum
diameter near closure 17 to a mimimum diameter near member 27. Conveniently,
the two filters may have the same apex angle. Filter 31 comprises a body
40 made up of pleated paper 41 between inner and outer protecting sheets 42
and 43 having large perforations to transmit air. By reason of the conical
configuration the pleats, which lie along lines defined by the intersections
with the conical surface of planes passing through axis 12, are more open
near the larger end of the filter. AT its smaller end body 40 is secured
in a disk 44 which closes the filter end except for a central aperture 45
to pass member 27 and the shoulder of a second wing nut 46 on member 27.
The larger end of body 40 is molded into an annular mounting member 50
having re~ilient portions 51 and 52 to engage closure 17 and step 20 respec-
tively. Member 50 also includes an outwardly directed lip 53 which resilient-
ly engages the annular wall of housing 11 for a purpose presently to be
described.
In order to prevent direct impingement of the air entering the
cleaner at 15 on a porous filter surface, a conical baffle 55 surrounds the
portion of body 40 near the larger end thereof. Baffle 55 fits on the end
of body 40 before member 50 is molded on, and has lugs 56 to aid in its
positioning and apertures 57 to pass the molding compound and ensure a good
support. Baffle 55 has a smaller apex angle than body 40, so that air can
move axially under the baffle from the right as seen in FIGURE 1, and the
effective cleaning area of the filter is not materially reduced.
At its end remote from member 50, baffle 55 is configured with a
bayonet joint 60 to engage a mating joint 61 in a separately molded fin
assembly 62 having a plurality of fins 63 extending angularly with respect
to axis 12. The primary purpose of fins 63 is to cause air passing generally
axially through them to have a vortical motion: this produces a centrifugal
33~i9
force by reason of which the larger airborne particles move outward to the
inner surface of housing 11 and thereafter move helically therearound
toward the open end thereof. Fins 63 also serve the secondary purpose of
holding filter 31 approximately centered while disk 44 is moved to bring
aperture 45 into alignment with member 27. Tightening of a wing nut 46
then holds filter 31 coaxially positioned in housing 11.
The open end 14 of housing 11 is closed by removable end cap 70
having a bead 71 around its end. A second bead 72 is formed near the open
end of housing 11, and a clamp ring 73 draws bead 72 against an 0-ring 73a
to hold the cap on the housing, the clamp ring being positioned axially
along the housing by a further bead 74, and being tightened by a suitable
fastener 75.
Cap 70 includes an annular partition 76, and the rim 77 of an
inner cup 78 is sized to fit between an inner lip 80 of partition 76 and
the outer rim 81 of disk 44 to prevent flow of air therebetween. A segmental
opening 82 is formed in partition 76 near its outer rim to permit particles
moving helically along the inside of housing 11 to pass into cup 70 and
become trapped. Rim 77 of inner cup 78 is extended axially at 83 over but
spaced from a portion of filter 31 to prevent any direct action of air flow
through the small end of filter 31 on the movement of particles into trap
70.
Turning now to FIGURES 6-8, an air cleaner 110 is shown to have a
housing 111 which is generally cylindrical about an axis 112 extending
between a closed end 113 and an open end 114. Housing 111 has a lateral
opening 115 near closed end 113, to which is fitted the usual inlet connection
member 116. Closed end 113 includes a permanent closure member 117 having
an annular inward step 120 and an axial opening 121 with a connection tube
122 fixed therein.
A support yoke 123 has a pair of legs 124 and 125 which diverge
to be secured to the inside of tube 122 as shown at 126: the yoke extends
along axis 112 and terminates in an axial member 127, externally threaded
~1:18369
at its outer end 128, which serves as the outboard support for a safety
filter 130 and a principal filter 131.
Safety filter 130 comprises a hollow porous body 132 having a
central axis of symmetry coincident with axis 112. Body 132 is conical,
tapering from a maximum diameter near end closure 117 to a minimum diameter
near member 127. The larger end of filter 130 is molded into a first
annular resilient mounting member 133 having an internal diameter to fit
over the legs of yoke 123. The radlally inward concave surface of annular
member 133 has a medial, outwardly directed circumferential groove 133a to
removably engage a bead 122a at the inner end of tube 122. A bevel 133b
simplifies the positioning of the filter on bead 122a. The axially outer
end of member 133 has a flattened surface 133c to sealingly engage end
closure 117 around opening 121 when groove 133a and bead 122a are engaged,
and has a radially outwardly extending lip 134. The smaller end of body
130 is molded into a disk 135 which closes the end of the safety filter ex-
cept for a central aperture 136 to pass member 127, and which has an axially
extending resilient lip 138 sealed securely against 127 by a spring clamp
137.
Principal filter 131 is also conical, tapering from a maximum
diameter near closure 117 to a minimum diameter near member 127: conYeniently
the two filters may have the same apex angle. Filter 131 comprises a body
140 made up of pleated paper 141 between inner and outer protective sheets
142 and 143 having large perforations to transmit air. By reason of the
conical configuration the pleats, which lie along lines defined by the
intersections with the conical surface of planes passing through axis 112,
are more open near the larger end of the filter.
At its smaller end, body 140 is molded into a first mounting
member 147 having first and second resilient portions 147a and 148: also
molded into member 147 is an axially short conical shield 149 spaced radially
from surface 142 and conveniently of the same apex angle. At its larger
end body 140 is molded into a second annular mounting member 150 having a
resilient portion 151 for engaging end closure 117 and further resilient
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portions 152a and 152b for engaging respectively annular step 120 of end
closure 117 and lip 134 of mounting ring 133.
In order to prevent direct impingement of the air entering the
cleaner at 115 on a porous filter surface, a conical baffle 155 surrounds
the portion of body 140 near the larger end thereof. Baffle 155 is molded
into mounting member 150, and has a smaller apex angle than body 140, so
that air can move axially under the baffle from the right, as seen in
FIGURE 1, and the effective cleaning area of the filter is not materially
reduced.
At its end remote from member 150, baffle 155 is configured with
a plurality of fins 163 extending angularly with respect to axis 112. The
primary purpose of fins 163 is to cause the air passing generally axially
through them to have a vortical motion. This produces a centrifugal force
by reason of which the larger air borne particles move outward to the inner
surface of housing 111 and thereafter move helically therearound toward the
open end thereof. Fins 163 also serve the secondary purpose of holding
filter 131 approximately centered in the housing while the open end of the
housing is closed.
This is accomplished by a removable closure member 170 having an
outer annular groove 171 to engage a bead 172 at the end of housing 111,
the ~oint being sealed by a gasket 173a. Closure member 170 has an annular
groove 184, with a step 185, to sealingly engage portions 148 and 147a
respectively of member 147. It also has a central aperture 186 to pass
member 127 and the shoulder 187 of a wing nut 188.
Housing 111 is provided, near its open end, with a lateral outlet
tube 190 for receiving particulate matter separated by centrifugal action.
As is well known in the art, this tube is provided with an evacuator valve
192 which permits gravity discharge of particulate matter collecting in
tube 190, by reason of vibration for example, without permitting significant
air flow into housing 111.
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Operation
In use cleaner 10 of FIGURES 1-5 i5 inserted in an air flow line
so that air, bearing undesired particulate matter in a range of sizes, can
enter the cleaner at 16 and leave it at 22. A æafety filter 30 is inserted
into the housing over yoke 23, so that its ring 34 seats against end closure
17, and its aperture 36 passes over member 27, and wing nut 37 is tightened.
A principal filter 31 is slid into housing 11, lip 53 and fins 63 engaging
the inside of the housing, until portions 51 and 52 of member 50 engage
closure 17 and step 20, and so that its aperture 45 passes over member 27
and wing nut 46 is tightened. Inner cup 78, which has been removed to
permit the emptying of particulate matter out of cap 70, is reinserted into
partition 76 in the end cap, and the cap is applied to housing 11, sealing
the space at the end of the filtering means, and secured in place by ring
73 and faætener 75. Note that now there is no passage for air from inlet
16 to outlet 22 except through the filters? a double seal being provided at
77-80-81, and a quadruple seal being provided at 11/53, 52/20? 51/17 and
34/17.
The cleaner is now ready to be put into operation, which is done
by drawing air through it. Air entering at 16 impinges on baffle 55, so
the particles are not driven into any filter surface. The air flows to the
right as seen in FIGURE 1, being given a circumferential component of mo-
tion by fins 63 which causes the larger particles to pass outwardly to
housing 11 and flow helically therearound until they reach partition 76 and
pass through opening 82 into end cap 70. Air containing smaller particles
passes radially through the axially central part of filter 31, and also
flows axially under baffle 55 and cup lip 83 so that practically the entire
surface of filter 31 is operative. After passing through filter 31 the air
passes through filter 30 and thence through outlet tube 22.
When a new filter 31 is in place, little particulate matter
reaches filter 30. As the period of use increases the pores in filter 31
become more and more clogged with particulate matter and the pressure drop
in the cleaner mounts to an undesirable level. When this occurs, it is
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necessary to interrupt the air flow through the cleaner, release clamp ring
73, remove end cap 70, remove wing nut 46, and replace filter 31. As the
used filter is drawn from the housing lip 53 scrapes from the inner wall
any particles which may have accumulated there, and draws them out of the
housing. Filter 30 is inspected, and is usually found in satisfactory
condition: if not, wing nut 37 is removed and filter 30 is replaced. Note
that for the usual case, where filter 30 is satisfactory, the outlet tube
22 is at no time open to the ambient atmosphere but is protected by safety
filter 30, hence the name of the latter.
Before reassembling the cleaner, inner cup 78 is removed from end
cap 70, and the particulate matter which has collected there is emptied
out. Reassembly is the reverse of disassembly, starting with the replacement
of cup 78 in cap 70 and concluding with tightening of fastener 75 of clamp
ring 73 and re-establishing air flow.
Cleaner 110 is inserted in an air flow line so that air, bearing
undesired particulate matter in a range of sizes, can enter the cleaner at
116 and leave it at 122. A safety filter 130 is inserted into the housing
over yoke 123 so that member 127 passes through aperture 136, and bevel
133b guides bead 122a into groove 133a. The filter is pressed firmly in
place and clamp 137 is expanded, passed over lip 138, and allowed to contract.
A principal filter 131 is now slid into housing 111, fins 163 helping to
guide the operation, until mounting member 150 prevents further insertion.
End cap 170 is applied over member 127 and wing nut 188 is tightened. Note
that there is now no passage for air from inlet 116 to outlet 122 except
through the filter, a triple seal being provided at 147a/185, 148/184, and
137/138 and a quintuple seal being provided at 152a/120, 151/117, 152b/134,
133c/117, and 133a/122a. The arrangement by which member 150 presses lip
134 against closure 117 is especially desirable, since it serves to maintain
the seal 152b/134, while allowing the fit between groove 133a and bead 122a
to be sufficiently relaxed to permit easy removal and replacement of safety
filter 130.
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The cleaner is now ready to be put into operation, which is done
by drawing air through it. The air entering at 116 impinges on baf$1e 155,
so the particles are not driven into any filter surface. The air flows to
the right as seen in FIGURE 6, being given a circumferential component of
motion by fins 163 which causes the larger particles to pass outwardly to
housing 111 and flow helically therearound until they pass through opening
189 into tube 190. Air conditioning smaller particles passes radially
through the axially central part of filter 131 and also flows axially under
baffle 155 and shield 149 so that practically the entire surface of filter
131 is operative. After passing through filter 131 the air passes through
filter 130 and thence to outlet tube 122.
When a new filter 131 is in place, little particulate matter
reaches 130. As the period of use increases the pores in filter 131 become
more and more clogged with particulate matter and the pressure drop in the
cleaner mounts to an undesirable level. When this occurs, it is necessary
to interrupt the air flow to the cleaner, remove wing nut 188 and
closure 170 and then remove filter 131 for replacement. Filter 130 is
inspected, and is usually found in satisfactory condition: if not, clamp
137 is removed and filter 130 is replaced. Note that for the usual case,
where filter 130 is satisfactory, the outlet tube 122 is at no time opened
to the ambient atmosphere, but is protected by safety filter 130, hence the
name of the latter.
Before reassembling the cleaner tube 190 is inspected and any
material which may have been trapped therein is removed. Reassembly is the
reverse of disassembly, starting with the replacement of the safety filter
and concluding with the tightening of wing nut 188 and re-establishing air
flow.
From the foregoing it will be clear thatthe invention comprises
an improved air cleaner wherein minimization of pressure drop and maximization
of precleaning efficiency, for any overall housing diameter, are accomplished
by constructing the filter elements with a conical configuration rather
3 E;~
than a cylindrical configuration, wherein there is provided improved sealing
together with means for automatically cleaning the inner surface of the
housing whenever a principal filter is changed, and wherein said improved
sealing is combined with ready and convenient replacement of filters, the
bead and groove principle being adaptable not simply for safety filters,
but for general use in air cleaner construction.
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